U.S. Pat. No. 7,385,506 granted to Shibata et al. discloses an optical-fiber-based perimeter security system. An optical fiber having Fiber Bragg Gratings (FBGs) is laid out at the perimeter of an area to be secured so that intrusion stretches the optical fiber and the FBGs in the optical fiber. FBGs reflect narrowband optical power around a center wavelength while transmitting optical power at other wavelengths. If the FBGs in the optical fiber are stretched, the center wavelength of the reflected narrowband optical power is shifted towards longer wavelengths. The magnitude of the wavelength shift is commensurate with the magnitude of the stretch. The wavelength shifts are converted into a time-varying electrical signal. The electrical signal is processed by a pattern recognition device for differentiating between true intrusion on the one hand, and false alarms due to wind and other environmental noise on the other hand. The required pattern recognition device may incur a substantial implementation effort.